The present invention relates to methods and apparatus for electro-optically scanning and/or reading symbols. The present invention is further directed to scanners which are preferably mirror-less, and their use with and/or incorporation into existing devices, such as cell phones, pagers, personal data assistants (PDA's), and the like.
In scanning and reading systems known in the art, a light beam is directed by a lens or other optical components along the light path toward a target, such as a bar code symbol. The light source is typically a gas or semiconductor laser. The use of semiconductor devices as the light source is especially desirable because of their small size, low cost and low voltage requirements. The laser beam is optically modified, typically by an optical assembly, to form a beam spot of a certain size at the target distance. A moving-beam scanner operates by repetitively scanning the light beam in a line, pattern or series of lines across the target by means of imparting motion to the light beam through use of a scanning component. Such mechanisms frequently employ a mirror disposed in the optical path of the light beam.
Bar code reading systems also include a sensor or photo detector which detects light reflected or scattered from the target symbol. The photo detector or sensor is positioned in the scanner in an optical path so that it has a field of view which ensures the capture of a portion of the light which is reflected or scattered off the symbol. This light is detected and converted into an electrical signal. Electronic circuitry and software decode the electrical signal into a digital representation of the data represented by the symbol that has been scanned. For example, the analog electrical signal generated by the photo detector is converted by a digitizer into a pulse or modulated digitized signal, with the widths corresponding to the physical widths of the bars and spaces. Such a digitized signal is then decoded, based on the specific symbology used by the symbol, into a binary representation of the data encoded in the symbol, and subsequently to the information or alphanumeric characters so represented.
However, conventional moving-beam scanners and readers possess certain disadvantages. In some laser scanning applications, mirror movements have been found to be undesirable.
EP 0 731 417, the disclosure of which is incorporated herein by reference in its entirety, describes and number of embodiments and ways of generating a scanning beam. For instance, EP 0 731 417 discloses arrangements that include oscillating mirrors, oscillating substrates which include the scanning beam source, and arrays of light sources that are activated in a way that mimics a scanning beam. With regard to the embodiment of EP 0 731 417 that physically moves the laser light generator within the device, there is disclosed a laser light-generating diode disposed on a substrate, the substrate being mounted on rotatable hinges within a relatively stationary housing.
U.S. Pat. No. 5,144,120 to Krichever et al., the disclosure of which is incorporated herein by reference in its entirety, discloses mirrorless scanners with moveable laser, optical and sensor components. More particularly, Krichever et al. discloses scanning devices that include a drive means for repetitive movement about an axis or in a plane within the device to effect scanning.
Although the abovementioned documents embody important advances in the art, incorporation of a means for imparting motion to the light beam generator itself, or to reflecting mirrors, (i.e.—the “scanning component”) into the scanner/reader itself adds size, cost and complexity to the device.
Thus, there is a need for a more compact and versatile scanner which is simply and inexpensively fabricated. Moreover, there is a need for such a scanner that can be easily incorporated into or associated with other devices.